1. Field of the Invention
The present invention relates to rendering a plurality of asynchronous players on a single visual display, wherein each player is capable of rendering moving images at an arbitrary frame rate.
2. Description of the Related Art
The increasing use of digital systems to process images has resulted in the availability of systems that are capable of processing a wide variety of image types, including moving images from video and film, and virtual worlds generated from animations of three-dimensional geometric data. In a system that only has to deal with one particular data type, for example, video frames at a rate of thirty frames per second, it is possible to implement digital processing circuitry that operates synchronously with the frame rate, and considerable optimisations are thereby obtained.
As digital systems become increasingly complex, it has become customary to display several images on a visual monitor at the same time. These images are typically single frames from several clips, whose contents are to be edited together to form a final scene. Sometimes these clips are from several cameras viewing the same scene, and it is known to display moving images from several synchronous clips at the same time, so a director can make a best choice as to which camera angle to use without viewing each one separately.
In a typical compositing environment, clips may be derived from several diverse sources, including various film and video formats, having different frame rates and resolutions. Known image processing systems require that these be converted into a common format before they can be freely viewed, mixed and edited together during the video editing process. Displaying clips having different frame rates, in particular, is not done, due to excessive demands that would be made upon the graphics rendering process in order to achieve this.
Graphics rendering is typically performed by a highly optimised graphical signal processing circuit. This has many levels of pipelining in order to ensure that maximum performance is achieved for a given amount of silicon circuitry. However, switching between clips in different formats requires that pipelines in the graphics circuitry are cleared, and this will incur a prohibitive performance penalty on systems that attempt to freely display several different formats of image data. Furthermore, when several players are used to display clips having different frame rates, the necessity to switch between the different players rapidly increases this pipeline clearing overhead, making such a system impractical or very expensive to implement. In known systems, therefore, only one format is displayed at a time. Multiple formats can be represented by still frames, and these may then be previewed at high quality by adjusting the system to deal exclusively with that format while it is being viewed or edited. High quality combination of image types on the same display is only done by explicit conversion into a common format prior to editing.